The role of opiate receptors located on catecholaminergic cells was studied using primary cultures of adrenal chromaffin cells. These cells contain opiate receptors in measurable amounts. Stimulation of these receptors with agonists decreases the releases of catecholamines elicited by nicotine. This effect is stereospecific and is reverted by naloxone and dyprenorphine. The results suggest that stimulation of opiate receptors modulates allosterically the function of nicotine and other receptors located on the chromaffin cell membranes.